light-atom anomaly

https://doi.org/10.1351/goldbook.L03523
A dynamical effect that arises for a process w
L03523.png
hen the species A is light (e.g. a hydrogen atom) compared to B and C . The vibrational excitation of the product A–B is low, since the light atom A approaches to within the bonding distance of BC before the C atom retreats. The energy of reaction is therefore released as repulsion between A–B and C , with the result that there is translational excitation of the products.
Source:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 171 [Terms] [Paper]